A typical LCD has the advantages of portability, low power consumption, and low radiation. Therefore, the LCD has been widely used in various portable information products, such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, the LCD is considered by many to have the potential to completely replace cathode ray tube (CRT) monitors and televisions.
FIG. 8 is a schematic, side cross-sectional view of certain components of a typical LCD. The LCD 10 includes a color filter substrate 11, a thin film transistor (TFT) substrate 12 positioned generally opposite to the color filter substrate 11, a liquid crystal layer 13 sandwiched between the two substrates 11, 12, and a common electrode layer 15 located between the color filter substrate 11 and the liquid crystal layer 13.
Referring also to FIG. 9, this is a schematic, abbreviated diagram of certain components of a drive circuit of the LCD 10. The drive circuit 20 includes a plurality of data lines 23 that are parallel to each other and that each extend along a first direction, a plurality of gate lines 24 that are parallel to each other and that each extend along a second direction orthogonal to the first direction, a plurality of pixel units (not labeled) defined by the intersecting data lines 23 and gate lines 24, a data driver 21 configured for driving the data lines 23, and a gate driver 22 configured for driving the gate lines 24. The data lines 23 and the gate lines 24 are located at the TFT substrate 12 of the LCD 10.
Each pixel unit includes a TFT 25, a pixel electrode 26, and a pixel capacitor 27. A gate electrode (not labeled) of the TFT 25 is connected to a corresponding gate line 24. A source electrode (not labeled) of the TFT 25 is connected to a corresponding data line 23. A drain electrode (not labeled) of the TFT 25 is connected to the pixel electrode 26. One electrode (not labeled) of the pixel capacitor 27 is connected to the pixel electrode 26, and the other electrode (not labeled) of the pixel capacitor 27 is electrically connected to the common electrode layer 15.
Referring also to FIG. 10, this is an abbreviated timing chart illustrating operation of the gate driver 22 of the LCD 10. The gate driver 22 applies a plurality of gate signals G1-Gn to the gate lines 24. Each of the gate signals is a voltage pulse signal. During each frame time T1, one gate signal is applied to the gate lines 24, one by one in turn. That is, at any given time during the frame time T1, only one of the gate lines 24 has a gate signal applied thereto. The period of time that each gate line 24 has a gate signal applied thereto is defined as T2. During the time T2 when the corresponding gate line 24 has a gate signal applied thereto, the transistors 25 connected to the gate line 24 are turned on. The data driver 21 applies a plurality of data signals to the data lines 23. Each data signal is transmitted to the pixel electrode 26 via a corresponding turned-on TFT 25. Thereby, the corresponding pixel unit displays a gray level according to the data signal.
Referring also to FIG. 11, this is an abbreviated timing chart illustrating operation of the data driver 21 of the LCD 10. Line “Vd” (the solid line) represents a waveform output by the data driver 21 during the period T2. “Vcom1” (shown as the dashed line) represents the common voltage applied to the common electrode layer 15. “R”, “G”, “B” respectively represent data voltages of red (R), green (G), and blue (B) data signals corresponding to red, green, and blue pixel units. The data voltages of the red, green, and blue data signals have a positive polarity and a negative polarity relative to the common voltage Vcom1. In particular, if the data voltages of the red, green, and blue data signals are greater than the common voltage, the red, green, and blue data signals have a positive polarity. If the data voltages of the red, green, and blue data signals are less than the common voltage, the red, green, and blue data signals have a negative polarity. As indicated in FIG. 11, a total voltage value of the data signals having the positive polarity is less than a total voltage value of the data signals having the negative polarity.
Parasitic capacitors (not shown) exist between the pixel electrodes 26 and the common electrode layer 15. Data signals applied to the pixel electrodes 26 can influence the common voltage via the parasitic capacitors. For example, if the total voltage value of the data signals having the positive polarity is less than the total voltage value of the data signals having the negative polarity, the applied common voltage Vcom1 is pulled down to a reduced common voltage “Vcom2”, as shown in FIG. 12. That is, the data voltages having the positive polarity are in effect increased in magnitude, and the data voltages having the negative polarity are in effect reduced in magnitude. This causes so-called crosstalk between the data lines 23 of the LCD 10.
What is needed, therefore, is a liquid crystal display that can overcome the above-described deficiencies, and a method for driving a liquid crystal display that can overcome the above-described deficiencies.